Flexible electric heating device



Sept. 7, 1965 'r. w. BULL FLEXIBLE ELECTRIC HEATING DEVICE 2Sheets-Sheet 1 Filed March 4, 1963 .BY MW; fihyu MOW Sept. 7, 1965 T. w.BULL 3,205,341

FLEXIBLE ELECTRIC HEATING DEVICE Filed March 4, 1963 2 Sheets-Sheet 2FIG.6

FIG.8

United States Patent 3,205,341 FLEXIBLE ELECTRIC HEATING DEVICE ThomasWilliam Bull, London, England, assignor to Electr'othermal EngineeringLimited, London, England, a British company Filed Mar. 4, 1963, Ser. No.262,437 Claims priority, application Great Britain, Mar. 5, 1962, 8,485/62 Claims. (Cl. 219-528) This invention relates to a flexible electricheating device.

For a better understanding of the invention and to show how it may becarried into effect, reference will now be made to the accompanyingdrawings, in which:

FIGURE 1 illustrates an electric heating element with interlocking loopsformed around it,

FIGURE 2 shows by means of an enlarged diagrammatic end view the loopsaround the element,

FIGURE 3 illustrates a stage in the construction of a flexiblecup-shaped structure or pocket incorporating the heating element, theloops being shown only diagrammatically,

FIGURE 4 shows the complete cup-shaped structure or pocket incross-section,

FIGURES 5 to 8 show different heating devices in the form of broadstrips or sheets.

FIGURE 1 shows an electric heating element 1 consisting of resistancewire 2 wound on a core 3, consisting of a cord made from glass threadsand covered with a helical wrapping 4 of glass threads.

FIGURES 3 and 4 are concerned with a flexible cupshaped structure orpocket which incorporates the electric heating element 1 of FIGURE 1 andwithin which a fiask or other vessel may be inserted in order to heatthe vessel. To make this structure, a length of the resistance element 1is fed into an overlook or overlocking machine such as is used toprovide a nonfraying edge in the manufacture of underwear. The machinehas four needles and is loaded wth four lengths of yarn consisting ofglass threads and is operated so that three of the lengths of yarnproduce interlocking loops around the element 1 as shown in FIGURES 1and 2, in which parts of the three lengths of yarn are referenced 5, 6and 7 respectively. FIGURE 1 shows to the left the loops as seen lookingin the direction of the arrow A in FIGURE 2 and to the right the loopsas seen looking in the direction of the arrow B. Three lines 8, 9 and 10of points of interlinking between the lengths of yarns extend along theelement and are unequally spaced around its circumference. The yarn ofthe length 5, for example, if of sinuous formation and extends from aninterlinking point in the line 8 half-way round the element to aninterlinking point in the line 10 and back again to an interlinkingpoint in the line 8 and so on. The loops made from the length of yarn 5are longer than the remainder. When a convenient length of the element,say two or three inches, has been covered with interlocking loops inthis way, the part 11 which was first covered with the loops is bentround to lie alongside the part 12 which has just been covered with theloops to form a circle as shown in FIGURE 3. The three lengths of yarn5, 6 and 7 are used to make more loops on the heating element,progressing in the direction of the arrow 13 in FIGURE 3, but here thefourth length of yarn 14, is also used and it forms loops whichinterlock with the loops (referenced 15 in FIGURE 3), which have alreadybeen formed from the length of yarn 5 on the part 11 of the element andwith the loops (referenced 16 in FIGURE 3) which are being formed fromthe length of yarn 5 on the element.

By continuing in the manner described above a fiat spiral of therequired diameter is obtained. However, the tension of the heatingelement being fed into the overlooking machine is so varied throughoutthe operation that when the flat circular sheet produced by thedescribed process is removed from the machine, in which it isrestrained, it adopts the shape of a cup, shown in FIGURE 4. In thisfigure the reference 17 represents a knitted band of glass yarns with noheating element in it and 18 represents a support wire secured to theouter edge of the band 17.

In the process described above, a narrow band with the heating elementrunning down its centre is continuously produced and at the same timeone side of the band is joined to the opposite side of a part of theband which was produced earlier. Instead of this, however, as the bandis being made in its spiral formation, one edge of a separate strip ofknitted or otherwise formed fabric comprising interlocking loops may besimultaneously joined to the radially outermost side of the band and theopposite edge of the strip is then joined to the inner edge of the bandas the next turn thereof is being made by interlocking loops. Byinterposing such a strip, of constant or varying width, betweensuccessive turns of the band in only one or more parts of the spiral, orby using a strip of varying width throughout the spiral, the heatproduced per unit area of the pocket may be varied as desired. Thisresult could also be attained by so making the heating element that itsresistance per unit length is not the same throughout its length.

A suitable machine for carrying out the process described above is anoverlook machine which is made mainly for overseaming, serging andhemming of garments by Union Special Machine Company of Chicago 10,U.S.A., and called by them Union Special Thirty Nine Fives or UnionSpecial Class 39500. The process can also be carried out on a twinneedle flat bed sewing machine, for example one made by the SingerSewing Machine Company.

It is well known to make a cup-shaped structure of knitted or wovenglass yarns and subsequently to attach an electric heating element toit, so that it takes the form of a spiral around it, by a separate handstitching operation. As compared with this, the process described abovewith reference to FIGURES 1 to 4 afford a considerable saving in timeand hence in production costs.

In the example illustrated in FIGURE 5, one band 20 is first made byforming interlocking loops of glass yarn around a heating element 1which is constructed as described with reference to FIGURE 1. The numberof lengths of glass yarn employed and hence the number of lines ofinterlinking points extending along the element, is three as before.Then a second band 21 is made and simultaneously attached to the band20, using three lengths of yarn to form interlocking loops around theelement of the band 21 and a further length of yarn 22 to form loopsinterlocking the loops of the two bands. The showing of the loops on thebands 20 and 21 corresponds to the left and right-hand halves,respectively, of FIGURE 1. By proceeding in this way, a heating devicein the form of a broad strip or a sheet can be obtained.

FIGURE 6 shows a heating device in the form of a broad strip consistingof four bands 23 to 26, formed one at a time, and joined together byinterlocking loops represented by the reference 27. Each band contains aheating element 1. By contrast, FIGURE 7 shows a heating deviceconsisting of six bands of which the outer two contain heating elements1 and the inner four contain spacer members 28, which may simply beglass cords, around which loops are formed in exactly the same way asthey are around the heating elements. FIGURE 8 shows a heating device inthe form of a broad 3 strip similar to that of FIGURE 7 but in which thetwo outer bands are replaced by one single band 32 containing a singleheating element 29, there being a reverse bend 30 in this band at oneend of the heating device. The bands between the two parts of the band32 contain spacer members 31.

It will be understood that in a heating device constructed as describedabove heating elements and spacer members may be used as appropriate toobtain any desired distribution of heat dissipation over the area of theheating device. If there are more than one length of heating element,these can be joined together in any desired series, parallel orseries-parallel arrangement.

The distance between adjacent stretches of heating element, and hencethe distribution of heat dissipation, can be varied by the use of thespacer members, by varying the diameter of the heating element and/orthe spacer members, by varying the tension of the yarns and by varyingthe rate of feed of the heating element and/ or the spacer members intothe machine.

I claim:

1. A flexible electric heating device comprising an elongated electricalconductor, loops of yarn extending transversely around said conductorand throughout the length thereof, said conductor having portionsdisposed adjacent to and spaced apart from each other, and a series ofloops of yarn separate from said first named loops and extending betweenthe loops of yarn of said adjacent conductor portions, said series ofloops being loops of yarn extending transversely of said conductorwholly therearound and extending throughout its length, said loops beingformed by a plurality of continuous lengths of said yarn, each separatelength of yarn having its loops interlocked with the adjacent loops,said conductor having portions thereof disposed adjacent each other inspaced apart relationship, and a further series of loops of yarnseparate from said continuous length of yarn extending between andinterlocked with said interlocking loops of yarn on said adjacent spacedconductor portions, said further series of loops being formed of acontinuous length of yarn extending :along the longitudinal dimension ofsaid adjacent conductor portions.

3. The heating device of claim 2 wherein said adjacent conductorportions are disposed in a spiral configuration.

4. The heating device of claim 2 wherein said adjacent conductorportions are disposed spirally in a cup-like configuration to form aheating device.

5. The heating device of claim 2 wherein said adjacent conductorportions are disposed parallel to each other and in the same plane toprovide a flat strip.

References Cited by the Examiner UNITED STATES PATENTS 869,460 10/07Richmond 219-46 1,213,656 1/17 Kinnard 66170 1,553,461 9/25 Negromanti.

2,157,606 5/39 Harris 66-193 2,482,665 9/49 Geyer 219529 2,643,324 6/53Goldstaub 219529 2,712,592 7/55 Goldstein et 'al 219-528 X 2,967,4151/61 Ford et a1. 66-193 JORDAN FRANKLIN, Primary Examine

1. A FLEXIBLE ELECTRIC HEATING DEVICE COMPRISING AN ELONGATED ELECTRICALCONDUCTOR, LOOPS OF YARN EXTENDING TRANSVERSELY AROUND SAID CONDUCTORAND THROUGHOUT THE LENGTH THEREOF, SAID CONDUCTOR HAVING PORTIONSDISPOSED ADJACENT TO AND SPACED APART FROM EACH OTHER, AND A SERIES OFLOOPS OF YARN SEPARATE FROM SAID FIRST NEMAE LOOPS AND EXTENDING BETWEENTHE LOOPS OF YARN OF SAID ADJACENT CONDUCTOR PORTIONS, SAID SERIES OFLOOPS BEING FORMED OF A CONTINUOUS LENGTH OF YARN EXTENDING ALONG THELONGITUDINAL DIMENSION OF SAID ADJACENT CONDUCTOR PORTIONS AND ACROSSTHE SPACE BETWEEN SAID PORTIONS TO INTERLOCK SAID PORTIONS TOGETHER.